This invention relates to a device for supplying electric power to a receiving assembly of great length containing a plurality of electronic assemblies distributed over its whole length.
More particularly, the invention concerns an electric feeding device for data acquisition apparatuses arranged at regular intervals along a seismic streamer. Each acquisition apparatus is adapted to collect seismic signals generated by different receivers or receiver groups placed in adjacent elements of a seismic streamer, in response to echoes, from various reflecting or diffracting sub-soil layers, of acoustic waves generated by a seismic source, and to sequentially transmit said signals to a receiving and recording system placed on a vehicle on reception of appropriate orders. Apparatuses of this type are described in the published French Patent Application No. 2,471,088.
The electric supply of the electronic assemblies contained in the seismic streamers may be effected, for example, by a DC voltage ge generator connected to said assemblies through electric feeding cables of great length. The electronic assemblies may be connected in parallel to said feeding cables either directly or through transformers adapted to transform the DC feeding voltage to another DC voltage of lower amplitude.
This feeding system has the drawback of ohmic losses through the feeding cables which are very often of great length, resulting in voltage drops which reduce the actual voltage supplied to the electronic apparatuses connected to these cables at locations remote from the electric current generator, in proportion to the length of the seismic streamer. Another disadvantage of the DC supply is the possible occurence of electrolysis phenomena when moisture results in water condensation on electric contacts.
The electric supply of the electronic assemblies contained in the seismic streamer may also be effected by a generator of AC voltage connected to feeding electric cables of great length. The electronic assemblies are fed through AC voltage transformers whose primary windings are connected in parallel onto the feeding lines. This feeding type has also the disadvantage, resulting from the internal impedance of the feeding cables, of voltage drops which are higher the longer the cables, so that the apparatuses of the seismic streamer which are at great distance from the generator of AC voltage are liable to be insufficiently fed with electricity.